I will admit I got a little misty eyed in the beginning when Kirk’s father dies saving his family (it happens in the first 10 minutes, so it’s not exactly a spoiler). That little event though kicked off a paradox that the film (and canon) has resolved by creating an alternate timeline. And I think that’s also fine. Take the universe in a different direction where Kirk was raised by an abusive father (again, first 10 minutes). It will lead to an universe of possibilities.
But the problem with alternate timelines is that they are just that: alternate. They branch out from their point of origin taking with them the element that created the alternate timeline (in this case Nero). <spoilers ahead> The sticking point for me with this is that future-Spock travels to this timeline from the original at a later time. Nero arrived in 2233, creating the alternate timeline; future-Spock arrives in the alternate timeline in 2258. The question is how? If you go to Star Trek Online, you can see a nice illustration showing the branching and when Spock arrives. But the problem is that Future-Spock didn’t just travel in time, he traveled between timelines. Think of it like driving down a road, following an evil genius bent on the destruction of the world. The two of you come to an exit that will leads to Fargo, North Dakota. The evil genius takes the exit, but you don’t. Instead you speed down the highway until you reach an exit that lead to Reno, Nevada, which you take. You’ve taken a different road. And no matter how far you drive along that road, it’s not going to intersect the Fargo exit. The same thing happens in time travel (assuming multiple timelines, time travel, etc.). Nero created one timeline with his trip (taking the Fargo exit), while future-Spock traveled to a point later in the prime timeline (the Reno exit), creating his own timeline. At no point would these new timelines intersect, at no point could one jump to another (except in a transporter accident but then Spock would have to grow a goatee). So how did Future-Spock end up in Nero’s timeline? The magic of bad plotting, I’d guess. It’s a nit-picky detail, but one that hit me when I saw the timeline image.
In reality (movie-wise) Nero would have appeared in 2233 and realized he was in the past. He would then go on a rampage with his powerful weapons (comparatively), destroying what he could until he calmed down or was defeated. Or maybe he’d realize he was in an alternate timeline and give the Romulans a big boost in technology by flying to the homeworld and giving them his ship.
Future-Spock, meanwhile, would have appeared in his new reality with a whole bunch of Red Matter (seriously, what was up with that? They couldn’t come up with a plot device?) and never encountered Nero. Maybe he would have traveled to that Galaxy-threatening supernova and dropped the Red Matter there, eliminating it as a threat altogether and then lived out his years on Vulcan (since he had already created a new timeline). Or maybe he would have looped around a star and traveled back to the future to minimize his effect on the timeline.
However it would have happened, I came away from the movie disappointed. Not by the plot points or the acting, but by the story on a whole. That and the lens flare really annoyed me.